1. The Field of the Invention
The present disclosure relates generally to display systems, and more particularly, but not necessarily entirely, to display systems that utilize pulsed laser illumination sources.
2. Description of Background Art
Advanced display devices are becoming more prevalent in modern society. Such display devices are used to display information in a wide variety of settings providing, inter alia, education and entertainment. There have been several recent promised enhancements to display technologies including: increased resolution, increased contrast and increased brightness levels as well as other characteristics that improve the overall quality of images produced with dynamic video display systems.
Technologies used to produce advanced video displays include: Texas Instruments' DLP® projector using a digital micromirror device (“DMD”), Sony's SXRD® system and JVC's D-ILA® apparatus both which incorporate liquid crystal on silicon (“LCOS”) technology, Kodak's grating electromechanical system (“GEMS”) as well as systems using grating light valve (“GLV”) technology. All of these particular technologies differ in the devices which are used to modulate the light which is projected, and such light modulation devices are at the core of each system and the component to which the rest of the system components surrounding them are designed.
Previously available display technologies have typically employed either a two-dimensional scan architecture or a column-scan architecture, sometimes referred to as a one-dimensional scan architecture, to form an image on a viewing surface. In a display device employing a two-dimensional scan architecture, the underlying light modulation device includes a two-dimensional array of pixel elements able to generate an entire frame of an image at one time. The two-dimensional array of pixel elements may include micro-electro-mechanical (“MEMS”) structures. Alternatively, the two-dimensional array of pixel elements may include liquid crystals, such as those incorporating LCOS technology. In a display device employing a column-scan architecture, the underlying light modulation device may include a one-dimensional array of MEMS pixel elements able to draw a single column of the image at a time. To generate an entire image on the viewing surface, the single columns of the image are scanned, one-by-one, across the viewing surface, by a scanning device, such as a rotating scanning mirror or oscillating scanning mirror. As used herein, a scanning device may refer to any device having a moving reflective surface operable to scan modulated beams of light onto a viewing surface.
In the past, the previously available display technologies incorporated a variety of different light sources. For example, some of the display technologies utilize an incandescent lamp for generating white light which is passed through a color wheel as the light travels to the surface of the light modulation device. The use of a incandescent lamp in a display system has drawbacks, including, the limited life of the lamp and the need for color filters or a mechanized color wheel to produce different colored light.
Other light sources for light modulation devices have, in the past, included continuous wave lasers. The benefits which accompany the use of the continuous wave lasers include the ability to eliminate the need for separating white light into primary colors and their high power output. However, continuous wave lasers are in some instances disadvantageous due to their high power consumption, complex technical design, and excessive heat output.
Recently, improvements in the operation of semiconductor pulsed lasers have made them more attractive for use as light sources in display devices that utilize light modulators. These improvements eliminate some of the problems associated with the use of lamps and continuous wave lasers. However, even with the benefits provided over the previously available light sources, the use of semiconductor lasers in a display device is still faced with significant challenges of its own.
For example, one drawback to the use of semiconductor lasers is that in order to achieve maximum light intensity, the semiconductor lasers suitable for use in a display device must operate at a relatively low duty cycle. Another drawback to the use of semiconductor lasers is that their power output is relatively low when compared with some of the continuous wave lasers that have been previously available.
Another previous drawback to the use of pulsed light sources, such as a semiconductor laser operating at less than 100% duty cycle, in display devices having a column-scan architecture has been that most such display devices have previously required a light source that produces continuous light, such as a continuous wave laser, in order to generate an acceptable image. That is, past attempts to use pulsed light sources in a display device having a column-scan architecture have been unsuccessful as the pulsed light sources caused noticeable irregularities in the displayed image.
In particular, as the columns of pixels are each scanned across a viewing surface from a display device using pulsed light sources, undesirable vertical stripes and interpixel gaps are visible in the image due to the pulsed nature of the light incident on the light modulator. A primary cause of these vertical stripes and interpixel gaps is believed to be the relatively short pulse time of the pulsed laser sources when compared to the time necessary to scan a column of pixels on a viewing surface. In some instances, the duty cycle of the pulsed lasers, the ratio of the duration of a laser pulse to the time necessary to scan a column or pixel, is less than 50%. This means that, in some cases, the pulsed lasers are only active for an interval which is less than one-half of the time it takes to scan one full column or pixel. The end result of the low duty cycle of the pulsed lasers is that an intensity drop occurs at the edges of the pixels in a column. This problem becomes even more apparent when two columns of pixels in adjacent columns are viewed side-by-side.
It would therefore be an improvement over the previously available technologies and devices to significantly reduce, or eliminate altogether, the irregularities caused by the use of pulsed light sources in a display device. It would be a further improvement over the previously available technologies and devices to significantly reduce, or eliminate altogether, the irregularities caused by the use of pulsed light sources in a display device having a column-scan architecture.
The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.